Filters are well-known in the electrical art, functioning as key building blocks in wireless communications and analog signal processing. Cellular communication devices are the largest consumer of filters. Nowadays, billions of these devices are produced every year and even a small improvement in cost and power consumption has a large impact. For example, consider a zero intermediate-frequency (zero-IF or ZIF) receiver. After reception by the antenna, a preselect filter selects a desired band (tens of MHz wide) containing the desired signal (from hundreds of kHz to several MHz wide) which is then amplified by a low noise amplifier (LNA), then downconverted by a mixer to baseband. Then, a sharp low-pass filter (LPF) selects the desired channel. The channel select filter is followed by an ADC. To relax the ADC dynamic range or the required effective number of bits (ENOB), the channel select filter usually has a high order.
There is thus a need for a passive filter that has very low power consumption to increase battery life, low noise to improve the overall noise performance of the system as well as good linearity to work properly in presence of interferer signals. Also, a high tenability is required for today's multi-mode/multi-standard radios.